Shareholders' Equity (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 08, 2015	Dec. 31, 2017	Dec. 31, 2016
Total risk-based capital:
Actual Regulatory Capital - Amount		$ 396,451	$ 368,856
Capital To Risk Weighted Assets		14.14%	14.04%
Minimum Requirement for capital Adequacy Including Capital Buffer Total Risk-Based Capital Ratio		9.25%
Minimum Regulatory Capital Required - Ratio		8.00%	8.63%
Tier 1 capital:
Actual Regulatory Capital - Amount		$ 357,261	$ 330,729
Actual Regulatory Capital - Ratio		12.74%	12.59%
Minimum Requirement for capital Adequacy Including Capital Buffer Tier I Risk-Based Capital Ratio		7.25%
Minimum Regulatory Capital Required - Ratio		6.00%	6.63%
Common equity tier I capital		$ 316,677	$ 296,120
Tier 1 leverage capital ratio:
Actual Regulatory Capital - Amount		$ 357,261	$ 330,729
Actual Regulatory Capital - Ratio		9.07%	8.83%
Minimum Regulatory Capital Required - Ratio		4.00%	4.00%
Common Equity Tier I Risk Based Capital Ratio		11.30%	11.27%
Minimum Requirement for capital Adequacy Including Capital Buffer Common Equity Tier I Risk-Based Capital Ratio		5.75%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets		4.50%	5.13%
Capital Conservation Buffer		2.50%
Value Of Trust Preferred Securities Included In Tier One Capital	$ 43,000	$ 43,000
Subordinated Debt	$ 15,000	$ 58,911	$ 58,755
Debt Instrument, Term	10 years	10 years
Subordinated Borrowing, Interest Rate	5.50%
Subsidiaries [Member]
Total risk-based capital:
Actual Regulatory Capital - Amount		$ 369,540	$ 340,908
Capital To Risk Weighted Assets		13.18%	12.92%
Minimum Requirement for capital Adequacy Including Capital Buffer Total Risk-Based Capital Ratio		9.25%
Minimum Regulatory Capital Required - Ratio			8.63%
Minimum Regulatory Provision To Be Well Capitalized - Ratio		10.00%	10.00%
Tier 1 capital:
Actual Regulatory Capital - Amount		$ 345,350	$ 317,782
Actual Regulatory Capital - Ratio		12.32%	12.05%
Minimum Requirement for capital Adequacy Including Capital Buffer Tier I Risk-Based Capital Ratio		7.25%
Minimum Regulatory Capital Required - Ratio			6.63%
Minimum Regulatory Provision To Be Well Capitalized - Ratio		8.00%	8.00%
Common equity tier I capital		$ 345,350	$ 317,782
Tier 1 leverage capital ratio:
Actual Regulatory Capital - Amount		$ 345,350	$ 317,782
Actual Regulatory Capital - Ratio		8.80%	8.54%
Minimum Regulatory Capital Required - Ratio		4.00%	4.00%
Minimum Regulatory Provision To Be Well Capitalized - Ratio		5.00%	5.00%
Common Equity Tier I Risk Based Capital Ratio		12.32%	12.05%
Minimum Requirement for capital Adequacy Including Capital Buffer Common Equity Tier I Risk-Based Capital Ratio		5.75%
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets			5.13%
Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets		6.50%	6.50%
Tier II Capital [Domain]
Tier 1 leverage capital ratio:
Subordinated Debt		$ 15,000
Minimum [Member]
Tier 1 leverage capital ratio:
Capital Conservation Buffer		1.25%